1. Field of the Invention
This invention relates generally to electrical selection of a desired transmission operating range or mode, and more particularly to a shift-by-wire system for placing and maintaining an automatic transmission in a desired operating range or mode.
2. Description of the Prior Art
A shift-by-wire system for manually controlling an automatic transmission for a motor vehicle would free valuable space in the interior of the vehicle conventionally occupied by the mechanical floor shifter assembly and replace it with a shifter switch solution that controls the transmission electrically. Conventional floor shifters are typically mounted on the instrument panel or the floor pan. A shifter switch is much smaller than conventional shifter and can be packaged in multiple areas of the interior within the reach of the driver.
A shift-by-wire system would provide further opportunities like “Auto Park” type features by electrically activating a shift-by-wire switch and controlling the transmission without need for mechanical activation of the shift lever as in a conventional system. A shift-by-wire system can also enhance customer passive safety by automatically engaging Park if the driver exits the vehicle without placing the transmission in Park mode.
Use of a rotary actuator mounted directly to the transmission must be engineered specifically for each transmission and may not be feasible in the existing package environment. Use of electronic or hydraulic actuation to shift the transmission range requires significant re-engineering of the transmission controls and investment expense.
Although multiple techniques are available for controlling the transmission to enable shift-by-wire selection of the transmission mode, a need exists in the industry for a system that provides electronic selection of the transmission range, that minimizes the degree to which existing transmission systems must be modified, and is applicable to a range of automatic transmissions, i.e., independent of the transmission type. The system should meet or exceed the safety requirements of current manual shifters and conventional shift-by-wire systems.